Guerilla (soliders who are not part of army) -warfare
militant (militia, a group of millitant)
ally/coalition (create a group of Nation to join together for command fight)

battle
conflict (a polite word for war)
war

offensive (when you attack)
counter- (the other side attacks back)
advance
repel (push you back)
incursion (enter the enemies territory, get inside)
onslaught destroying/killing a lot of people without pardon, raid)

boots on the ground (send soldiers into territory on the ground)
ground forces (walking in guns, knife, RPG)